Null Set
by Kalinga
Summary: Set right after Sensui's death and the end of Chapter Black. AU, I suppose, but it's fairly canonical, I just haven't seen any episodes after that.
1. Default Chapter

Koenma raised his eyes from the empty glass, having drunk as much as would be allowed. He was a fugitive, now. What else could he do but drink? In the human world, he stayed hidden, both from his father and from humanity itself. There was not much else to do when one has to be invisible to society's eye. Even with his dislocation from the underground where he once thrived, rumors had come to him, as they always did.

Hundreds of years, thousands maybe, since he had taken up the guardianship of the Earth. It was not a voluntary decision, but rather thrust on him by the necessity of his times. He would not lie to the empty glass: he had taken his father's deal for the amnesty it offered. This time, however, the past haunted him. Before he was guardian of the Earth, before he had the pacifier put in to limit and subdue his own power.

Sensui had not terrified him the way the memory of his own acts had. This was something new.

He knew Sensui would hardly be the last threat to this fragile domain. He had not expected the evil that came forth. The tyranny that would rain down from the demon world to envelop this one.

Sensui, for all his philosophical meandering, had committed a grave error in the end.

There was one person who he could ask for help. He looked into the glass again, considering another shot.

It had been a long time since they had last met.

And ironically, it was on the battlefield, fighting to the desperate truce to save this very planet that they had separated.

Koenma sighed. He had cut off all communications with his little band of brothers since Sensui's fall. He needed to think, he told them, and he needed to think alone.

Now, however, he was certain that it had been fear that had driven him to his solitude. Fear that the great battle, the _ragnarok_ of these times, had yet to come. Sensui, precocious as he was, had no idea he would be the herald, not the ending.

His secret was finally unraveling. His past stared him in the face, mocking him in the dirty glass he held. It was time to use the past, his past, to save the future of this world. _Where now do I go,_ he wondered, tapping his fingers rhythmlessly on the table. It seemed a futile question to ask.

There was only one place to go, after all. Only one person he could turn to, now, when his cards were down.

The question, of course, was whether the person he needed still existed on this side of the universe.


	2. Chapter 2

The sun was barely beginning to cut swaths in the dusky sky of dawn when he opened his eyes, looking carefully at the world that surrounded him. Even after all these years of exile both enforced and self-imposed, the world was still frighteningly fresh to him. He stared at the ground, weed-ridden and overgrown with spilling plants from the forest that loomed dangerously to the west.

Slowly, with a sure hand, he reached out to his weapon, always on his right hand side, always ready for battle that seemed to never come. It had been millennia since he had last drawn a weapon, and he had sworn never to use it again. But his unease was clouding his sense of duty to his oath. He grasped the thing firmly, and brought it in front of his face, staring at a single point of focus.

It was an enormous sword he held, seven feet long from tip to tassel, and sharpened on the stones of hell. It would never break, and its master, similarly, could never be broken. Balancing the blade on his fingers, he closed his eyes, slowly sinking into awareness. _Only understanding will save you now_, he thought to himself.

He had felt the shaking, and the breaking, of the world when Sensui had torn open the tunnel into the demon world. It had not disturbed him in the least. Sensui's dealings had nothing to do with his turf in this human land. Demons did not scare him. The most powerful were also the most intelligent, and the most intelligent had heard rumor and round of the strange zone in the human lands where spirit energy drained away, where those who utilized the energy of the soul were left unarmed. He had sealed off his terrain from the spirit energy of the world and intrusion. Invisible on any map the spirit world administration would make, and dreaded myth among the demons, it had been this way for years. Life created its own energy: that was enough to sustain him and his environment.

The break Sensui caused, however, had disturbed something primeval, he realized. Spirit energy had been streaming from cracks in the dull face of the earth for a time now. An older power was coming up from the hells of the underworld to meet him.

_I know your name_, he thought to himself. _Your purpose is still my mystery._

He opened his eyes again, calmer now. He was no guardian, and yet he loved the life of the world too much to flee the coming danger.

_So, my old friend, we meet. _ He could remember the days of danger, and the final battle which had kept the fragile hope of the world alive. Yet he had seen his future, and always, there was a voice. _Your sword is your life, and your life is your destiny._

There was a cold finality about that statement. He stared resolutely at the ground. There was one more piece of this puzzle that had yet to reveal itself.

There had been two who had defied and defiled the tradition of the spirit realm. There had been two warriors who had cast their honor to the dust and bled with their enemy as they locked him in the eternal prison.

_Koenma, you are needed once again. _


End file.
